The present invention relates generally to weather radar systems and particularly to airborne doppler radar systems used to predict potentially dangerous wind shear conditions in the flight path of the aircraft.
Microburst wind shear is one of the most serious hazards of aviation, and is particularly dangerous to heavily loaded jet transports flying low and slow on final approach or on takeoff before a comfortable margin of airspeed has been established. Pilots and engineers have learned to expect and deal with the nodal changes in horizontal winds as an aircraft descends. A microburst is different however and re,ires a very different response.
Typically a microburst is of very short duration and covers a small space geographically; the core of a microburst may be as small as 1 nautical mile or less in diameter. It appears suddenly, develops its dangerous potential and dissipates in a matter of minutes.
Early attempts to protect against this phenomenon included the development of a low-level wind shear alerting system. This alerting system consists of wind direction and velocity sensors around the perimeter of the airport., plus a central sensor. Data from the sensors are computed and displayed in the control tower and controllers then advise the pilots concerned. The information derived is seldom specific enough to justify aborting the takeoff or landing and the microbursts can sometimes pass undetected between the sensors or occur outside the sensor network.
Other efforts have resulted in wind shear warning systems aboard the aircraft. Presently systems are available which look at the inertial instrumentation and flight performance information aboard the aircraft and provide a warning when the accelerations experienced could be conducive to wind shear. These systems are called "reactive" systems because they detect hazardous flight conditions as the aircraft enters the wind shear condition. The problem is that reactive wind shear detection may not provide the pilot with enough time to successfully escape the dangerous condition.
A serious problem faced by airborne radar wind shear warning systems that are viewing the airspace in the aircraft glide path is how to deal with ground clutter. When ground based radar wind shear warning systems are used the ground clutter problem may be dealt with more easily since the ground clutter is essentially stationary. For example, with ground based radar a ground clutter map may be made periodically and then subtracted from the radar information. However, with airborne radar the ground clutter is seen in the primary antenna beam and is constantly changing.